Rotatable control



J 1954 A. A; LAHTI ROTATABLE CONTROL Filed Aug. 14, 1950 FIG. I.

Va i All FIG.3.

INVEN TOR. AR l O A. LAHT/ A T TOR/VE' Y Patented June 8, 1954 ROTATABLE CONTROL Arvo A. Lahti, Pasadena, Calif., assi nor to (ionsolidated Engineering Corporation,

Pasadena,

Calif., a corporation of California Application August 14, 1950, Serial No. 179,190

11 Claims. 1

This invention relates to improvements in rotatable controls, such as those employed in instrument panels to adjust the settings of a potentiometer, condenser or other adjustable apparatus disposed behind the panel and aims to avoid accidental disturbance of a setting when once it is made.

It is common practice to mount control knobs on instrument panels. The knobs may be struck accidently and thereby change the setting of the apparatus they control. To avoid these accidental movements, which if undiscovered will vitiate results obtained with the instrument, it has been proposed to provide the control knobs with locks, which usually are turned by a key or a tool such as a screw driver. It has also been proposed to mount the control knobs in recesses in the panel to prevent inadvertent movement of the knobs. It has also been proposed to place a protective cover over the control knob. None of these proposed solutions to the problem is entirely satisfactory, for they interfere with easy operation and adjustment of the instrument. 7

I have developed an improved control knob assembly in which the knob is rotatably mounted in the panel. The rear of the knob is attached to the apparatus that the knob controls by a compression spring which bridges a gap between the rear of the knob and the shaft of the apparatus which the knob is expected to turn. The spring preferably is a coil compression spring. The rear of the knob also has a lateral projection, preferably a flange, which is pressed against the rear face of the instrument panel by the spring and thus locks the knob to the panel. The face or front of the knob may project from the front of the instrument panel or be recessed therein, but preferably is flush with the panel when the apparatus is at rest. To change the setting of the apparatus, the operator presses the knob inward to disengage the locking projection on the rear of the panel and then turns the knob to the new setting. When the knob is released the instrument setting is again locked.

In summary, the control of the invention comprises essentially a finger-operated knob journalled in a control panel and coupled to the rotatable shaft of an apparatus to be regulated by a compression spring. The compression spring axially loads the knob, causing a braking surface at the rear of the knob to engage the inner surface of the panel, thereby providing a lock.

The apparatus of the invention will be more j 2 clearly understood in light of the following detailed description and drawings, wherein:

Fig. l is an elevation, partly in section, of a presently preferred embodiment of the control of the invention;

Fig. 2 is an exploded View of the control of Fig. 1; and

Fig. '3 shows a modification of portions of the apparatus shown in Fig. 2.

The apparatus of Figs. 1 and 2 comprises a cylindrical shaft l0 coupled by a compression coil spring H to a control knob l2 journaled in a round hole of a panel [3. shaft is fastened by a screw [5 to a shaft of a potentiometer It.

The knob consists of an inward projecting stub or shaft It, a centrally placed flange or projection I 9 having a greater diameter than the hole or journal in the panel, and a round button 2! journaled within the hole with its outer face flush with the outer surface of the panel. The button carries a washer 23 made of a material, say rubber, having a high coefficient of friction relative to the panel. The inner face of the washer abuts the flange and the outer face engages the panel in the locked position illustrated in Fig. l.

The coil spring, which is under compression, forces the flange and washer outward into engagement with the inner surface of. the panel, forming a friction lock which prevents inadvertent turning of the button.

The coil spring has an inside diameter greater than the diameters of the two shafts I0, I 8 which it couples together. The two ends of the spring are bent at right angles to each other and to the spring itself, forming two terminals 24, 25 which pass through the longitudinal axis of the spring. These terminals are respectively inserted into two holes 2%. 2! of the two shafts. This manner of coupling, because it allows radial freedom of motion between the two shafts, permits some misalignment of the two shafts along either ordinate of a plane lying parallel to the plane of the panel, without interfering with the rotation of the potentiometer.

To regulate the potentiometer, an operator places his thumb on the button and pushes inward, moving the washer and flange away from the panel. The operator can then rotate the control to the desired setting. After making the setting, the thumb is removed and the spring returns the rubber washer into contact with the panel, again locking the control.

Accidental operation of the knob is not prob- The other end of the able, because the button is tiltable in the hole so that a central axial pressure is required to release the friction lock. Depression of one edgeof the knob will not release the lock because the far edge will remain in contact with the panel.

In another modification of the control of the invention, the two shafts which are coupled togetherby the compression spring are provided at their adjoining ends l, [8' with mating coaxial couplings as shown in Fig. 3, which are spaced apart when the control is in locked position but which couple when the knob is pressed inward.

I claim:

1. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable knob journaled in the panel with a lateral projection of the knob engaging the inner surface of the panel, and a compression spring disposed behind the panel and coupling the shaft to the knob and forcing the projection of the knob outward into engagement with the inner surface of the panel.

2. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable knob tiltably journaled in the panel with its outer face substantially flush with the outer surface of the panel and with a lateral projection of the knob engaging the inner surface of the panel, and a compression spring coupling the shaft to the knob and forcing the projection of the knob outward into engagement with the inner surface.

3. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft,

projecting toward the panel, the combination comprising a rotatable button journaled in a hole of the panel, a flange having a greater dimension than the hole joined to the button inside of the panel, and a coil spring disposed behind the panel connecting the shaft to the flange and button and forcing the flange into contact with the inner surface of the panel.

4. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a tiltable button journaled in a hole of the panel, a flange having a greater dimension than the hole joined to the button inside of the panel, a washer made of a material having a high coefficient of friction relative to the material of the panel and larger than the hole, the washer being carried by the button with its inner face abutting the flange, and a coil spring connecting the shaft to the flange and button and forcing the washer into contact with the rear of the panel around the hole.

5. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable button journaled in a hole of the panel, a flange having a greater dimension than the hole joined to the button inside of the panel, a first control shaft extending inward from the flange and the button and joined thereto, a second control shaft connected to the shaft of the apparatus and spaced from the first control shaft, and a compression coil spring coupling the two control shafts together so that they rotate together and forcing the flange into contact with the inner surface of the panel.

6. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable button tiltably journaled in a hole of the panel with its outer face substantially flush with the outer surface of the panel and with a projection of the button engaging an inner surface of the panel, a first control shaft extending inward from the button and joined thereto, a second control shaft connected to the shaft of the apparatus, and a coil spring coupling the two control shafts together and forcing the projection into contact with the inner surface of the panel.

7. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable button in a hole of the panel with a lateral projection of the button engaging the inner surface of the panel, a first control shaft having a transverse hole and extending inward from the button and joined thereto, a second control shaft having a transverse hole connected to the shaft of the apparatus, and a compression coil spring disposed behind the panel with its two ends bent inward at right angles to each other connecting the two control shafts together and forcing the projection into contact with the inner surface of the panel, said ends of the spring being respectively inserted into the two holes of the two control shafts.

8. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable knob journaled in the panel with a lateral projecting of the knob engaging the inner surface of the panel in the locked r position, and a compression spring disposed behind the panel coupling the shaft to the knob and forcing the projection of the knob outward into engagement with the inner surface of the panel, the knob being spaced from the shaft to permit axial movement of the knob toward the shaft with the compression of the spring, thereby moving the projection away from the panel and releasing the lock.

9. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable button journaled in a hole of the panel, a flange having a greater dimension than the hole joined to the button inside of the panel and engaging the rear of the panel in the locked position, a first control shaft extending inward from the flange and the button and joined thereto, a second control shaft connected to the shaft of the apparatus and spaced from the first control shaft in the locked position, the adjoining ends of the two control shafts being provided with mating coaxial couplings disposed to couple with the control in an unlocked position, and a coil spring coupling the two control shafts together and forcing the flange into contact with the rear of the panel in the locked position and compressible to permit the axial movement of the first control shaft and its coupling into engagement with the coupling of the second control shaft, so that both control shafts rotate together.

10. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable knob extending within a hole which passes through the panel and having a lateral projection for engaging the inner surface of the panel, resilient means for forcing the projection of the knob against the inner surface of the panel, and means coupling the knob to the rotatable shaft for causing the shaft to rotate substantially in unison with the knob when the knob is moved inwardly toward the rotatable shaft and rotated. I

11. In a control for an apparatus mounted behind a panel and provided with a rotatable shaft projecting toward the panel, the combination comprising a rotatable knob extending within a hole which passes through the panel and tiltable on its axis of rotation, the knob having a lateral projection for engaging the inner surface of the panel, the shaft and knob being spaced apart, and

resilient means located behind the panel flexibly coupling the knob to the rotatable shaft and forcing the projection of the knob against the inner surface of the panel and also causing the shaft to rotate substantially in unison with the knob when the knob is moved inwardly toward the rotatable shaft and rotated.

References Cited in the file of this patent Number Number UNITED STATES PATENTS Name Date Graham Mar. 26, 1861 Bailey Apr. 2, 1889 Johnson Aug. 29, 1899 Barr Aug. 18, 1914 Clark Dec. 28, 1915 Rice Sept. 26, 1916 Winning Feb. 23, 1926 Saar Aug. 18, 1936 Galter Sept. 3, 1940 Newman Sept. 1, 1942 Siedle May 16, 1944 Jefirey May 2, 1950- Larson May 15, 1951 Schostak July 24, 1951 Best Aug. 28, 1951 FOREIGN PATENTS Country Date Norway Dec. 12, 1921 

